Hi,

I need some help with a 4 stroke. I got some help a couple of days ago to get it to fire. I was able to get it running but it wont stay running without the glow plug attached. It also seems to backfifre at times and the prop nut loosens.

Any help would be appreciated.

jon

It sounds like it is too rich on the low end needle. Please post what make and model it is, and we can get it set to factory settings with a little research. And don't run it without a locknut! You need two nuts on a four stroke!

They will also backfire and spit the prop if they are too lean.

You could also have a bad glow plug. Sometimes they'll glow with power hooked too them but they won't maintain the catalytic reaction to stay hot when you take power away.

Hi,

Thanks for the reply. It is a Magnum XL 91.


jon

Thanks.....Ive seen this way also....everyone said i was mad to toss the plug,,

flynte

im with Deadeye on this one

Usually, a backfire is caused by running too lean. And as ChuckW said, glow plugs CAN be bad even though they still glow.

OR... the plug that is in it might not be the right plug.  4-strokes MUST have a special glow plug made especially for 4-stroke engines

Replace it with an OS "F" plug

More probably to lean rather than to rich. I use a few of the Magnum 4 strokes and have found that the Fox Miracle plug works as well as any other 4 stroke plug and seems to last longer than the OS's do. Also check for oil content of the fuel, to high an oil percentage could be causing some of your problem. I have also had better luck with the lower nitro ratios, typically 10% seems about right.

jon, what engine is? do you have the 4 stroke plug on it?. If you remove the spark plug do you see it wet?. tell us more.

I had a Saito 180 that did this.. It ended up being the low end too rich. My engine is upside down and was dumping to much fuel on the plug and cooling it down to much. We leaned it out and she runs better than ever.

Jon :

Not being smart, just making a point.


The GLOW PLUG stays in the engine, the Glow Plug IGNITER is removed when the engine starts.


Minnflyer : My friends and I have been using the "FOX " Mirical plug in 4 strokes for years and they work just fine, and cost a lot less.
ENJOY !!! RED

what brand is the engine they all have a little different needle settings, BTW the cleaner the carb is the more responsive it will become to adjustments, if the engine has sit for a while the carb can get fouled by gum deposits making for sluggish results when your trying to get it tuned properly.

another thing is to (sure to be bashed for this) get a tachometer, http://www3.towerhobbies.com/cgi-bin...?&I=LXPT31&P=0 its helpfull for tuning a 4st engine, if you haven't worked with one before, finding the low and high end of the RPM range is important when tuning a 4st and can be tricky if you haven't done it before

I posted this in the other thread but it definatly applies here to this topic as well.